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07-10-2008, 04:32 PM #1
OT: Ever change the brakes on your forklift?
We have an old Yale that needs brakes. I wish I had a model number or something, but there doesn't seem to be a tag anywhere.
The riggers were here recently and said if I can do the brakes on my car, then a forklift should be no problem. OK, I'm not afraid of doing the brakes on my car...
Then he said "Oh, you have the kind where the whole axle has to come out" right before he left. So if I can attach this picture correctly, can anyone tell me what kind of mess (if any) I'd be getting myself into? Does the axle coming out mean bearings and all other kinds of things?
07-10-2008, 06:53 PM #2
Yes the cap/ axle needs to come out. Then a lock nut, then the wheel will fall off.
Brakes are a must on a truck
07-10-2008, 06:54 PM #3
fork lift brakes
No problem, But before you condemn the brakes that are on there, learn how or find an old mechanic that knows how to adjust brakes.I am familiar with the "old" Yale fork trucks up to 15,000lb and through the mid 70's they had brakes that had to have the proper shoe clearance to the drum maintained as the linings wore down.You can verify this type by looking at the backing plate to see if there are 2 fairly large (3/4???) hex headed "bolts"--one in front and 1 in back at about the 4 o'clock and 8 o'clock position for each wheel.These are NOT bolts but a means to rotate a cam like stop behind each shoe that keeps it nearly in contact with the drum when the brake is released.If I remember correctly the adjust procedure goes like this; Get both wheels just clear of the ground--rotating a wheel by hand to feel rolling resistance, place a wrench on an adjuster and advance it (I think the adjuster turns downward to tighten)until the wheel is harder to turn or you hear shoe contact, then back it up just slightly until it is eased--do this on all 4 adjusters and you may not have to pull a drum/wheel.If the shoes have to be exposed like for cleaning/replacement no problem.Removing the bolted plate will allow the axle to pull right out and expose a large bearing retaining nut that loads the wheel bearings.removing this nut allows the wheel/tire assembly to be removed along with the brake drum.These old yales were simple and durable old things and the drive axle was about identical with truck axle arrangement.Unlike some others with a reduction gear after the ring gear but the speed reduction before the ring gear required larger brakes and axle shafts.
07-10-2008, 07:06 PM #4
Firstly, I'd recommend getting a maintenance book on your machine. It is worth it, and eBay usually has them floating around for common machines like Yales.
One thing I'll recommend when doing forklift brakes is taking the opportunity to go to DOT 5 brake fluid. I've done at lest eight forklift brakes all the way through, up to 20,000 lbs capacity lifts. I have been very happy with DOT5 fluid in them. The master and slave cylinders stay bright inside and the silicone DOT5 doesn't draw moisture into it like DOT3.
One of our forklifts has a HydroVac unit on it, and that makes it have some serious brakes compared to just pedal-pressure. Another one I worked a HydroVac into its system, and it's also nice. Another two of them are just plain pedal brakes, and they are okay. One of our forklifts has air brakes. I think I've died and gone to heaven when I'm on it.
07-10-2008, 07:46 PM #5
Yes, the first technique involves jacking up the forklift...and the best part is you don't need a jack!
First order of business is to loosen the lugnuts...I twisted off a 1/2" sq drive ratchet attempting this, eventually got into the 3/4" sq drive hardware. Then, tilt the mast fully back, then crib up both sides under the bottom of the mast-channels. The forklift has "power forward tilt" and so it will lift itself off the ground. You will probably have to make a couple of incremental tries at this, when it is fully "up" then start blocking under the forward end of the frame rails, just in back of the front wheels where you'll work. Finally the truck will be up off the ground, safely on blocks on both sides.
The forklift at upper left had the "final drive cases" as part of the brake asm. The final drive is an internal ring and pinion spur gear setup that requires grease lubrication.
On one side of my forklift, the brake drum itself had ~5 lbs of grease in it, I mean packed solid. I chose to err slightly on the low side of the new grease pack I put in there in order to prevent contamination of the brake drum on the other side of the casting. The shaft penetration does not have a seal, merely a clearance bore ~1/8" diameter larger than the shaft. Basically I drive my forklift around the shop idling around at the lowest speeds (as opposed to a truck dock, or a material handler or line stocker job which would be constant high-speed motion), and so I rationalized I'll not likely wear out the ring and pinion with slightly less grease. I also feel like the MoS2-doped greases of today are better than the original formulation of ~25 years ago at the time the machine was originally built.
The brakes on this forklift use a very simple adjuster. It is a "finger" which is captured between a nut and a bolt. The finger holds the top part of the brake shoe where it is acted upon by the wheel cylinder. Essentially, the bolts are tightened to a torque where the wheel cylinder's hydraulic pressure acting on the pistons can overcome the friction and turn the finger outward as the shoes wear. However, the friction cannot be overcome in reverse by the action of the return springs, and so the finger stays where it was put until moved further by additional wheel cylinder action. The "fingers" are chrome plated I think so they don't seize/corrode/stick to the backing plate and so the brake shoe doesn't wear out the contact point as easily. They were in great shape.
I ended up sourcing a new brake master cylinder and new wheel cylinders while I was at it, blew out all the brake pipes after a solvent bath and put it all back together. The pads took a little "breaking in" but are working great now.
I had originally thought about DOT5 fluid, in fact posted about it...but after I see how easy it is to bleed the system, I think I'll just go with flushing it every 5 years or so.
07-10-2008, 07:55 PM #6
If you can spare the time to have the wheels/drums off the unit, you'll be 'playing safe', and be grateful later that you did.
Its really common on those older units to find that the seal for the wheel bearings has 'wept' enough oil/grease over the years to have the brake frictions well and truly greased.
Blocking up the machine just enough so that the wheels turn freely (on an old Clark you can do that by putting steel blocks under the fork frame, then tilting forward.....dunno about your Yale), have the axles out (be prepared to cut new gaskets, an easy job), bend the lock-tab to allow the retaining nuts for the axle bearings to be removed, then the wheel/drum assembly should slide off.
Removing the brake linings to clean them should be pretty much self-explanatory....mark them for position first, tho, so that they will go back exactly whence they came.
Clean the bearings well, and give them a good visual inspection for wear.....they'll probably be alright, but if you see signs of fretting anywhere, its best to fit new ones. Fit a new seal, any good bearing supply house should be able to match up the bearings and seals.
If you have a clutch/brake rebuilder in your area who could fit new friction linings to your brake shoes, and 'arc' them to the diameter of your drums, that would be best, of course, but you may have plenty of actual friction material still left on the existing shoes, so a really good cleaning may suffice. (thats a 'time v. $' decision)
Cleaning brake shoes is surprisingly tedious....lacquer thinner soak, then gentle heat....do this outside, obviously....after no more oil emerges from the friction material, de-glaze it with, say, 180 or so grit emery cloth. Likewise, de-glaze the interior working surfaces of the drums.
If your brake linings are wet with brake fluid, then there's nothing for it but to hone the wheel cylinders, and fit new cups......the cups are inexpensive, and available from any clutch/brake supply house.
07-10-2008, 07:58 PM #7
Carla brought up a good point...its a horribly messy job if the brake drum is contaminated by grease, mildly messy if not. I get a little worried about the possibility of asbestos in the wear debris and so I like to keep the parts "wet" until they are completed and ready for reassembly in order to keep dry particles from floating about.
A parts washer is almost paramount.
07-10-2008, 10:14 PM #8
Here is what I got out of the Clark (as described above). The long studs go thru holes cast into the transmission housing and unbolt from the center....requiring swivel sockets and flex-handle ratchets to undo.
The brake drum is splined to the shaft in question, retained by a snapring. The outer shallower spline engages the final drive in the transmission, there's an oil seal for trans fluid on the shiny spot.
The internally ring-geared hub for the outer final-drive reduction is on the opposite side of this flange. The road wheel bolts to that hub.
Also, the old brake shoes were barely worn...due to the internal lubrication on one side....but I replaced them anyway, had pre-ordered the parts and at the price paid, was not worth fooling with the old ones.
07-10-2008, 10:23 PM #9
Last thing...sorry for so many posts...my forklift also had an "inching" feature...that's what the manual called it.
This was a separate pedal on the left side which had its own master cylinder full of brake fluid. The fluid pressure from the LH pedal actuated the brakes plus actuated a piston that puts the automatic transmission into neutral. (There was also a shuttle valve involved so the two master cylinders simply didn't overfill each other).
I eliminated this system and went straight from the RH pedal to the brake wheel cylinders.
Here's why: 1. the forklift got a lot smoother in loaded operation, I have no more "clunks" from the clutches applying every time the LH pedal is released. 2. Another point of this system is so that the engine rpm can be raised so the mast can be quickly lifted as in warehousing. Used in that manner without putting the trans in neutral generates a lot of internal heat from fluid shear in the torque converter as it runs in "Drive" against the brakes. I rarely use more than the freelift in the shop operations, and I rarely am in such a hurry to raise the mast that I use more than the idle speed. I can always manually select neutral if I want to do some engine revving. 3. I saved on not having to replace these parts.
07-10-2008, 11:45 PM #10
Did a wheel cylinder on the Allis Chalmers at the museum. Just like an old Chevy truck drum rear. Only difference was that the brake system on that one was filled with hydraulic oil, not usual brake fluid.
07-11-2008, 12:15 AM #11
Wait.......old forklifts have BRAKES ???
I do think there's merit in using Hydraulic fluid instead of brake fluid in such applications.
Actually in any that have little to no possibility of
boiling the fluid, as brake fluid draws moisture and oils do not. Things will probably last longer with the oil....no 5 year bleed out required.
07-11-2008, 05:29 AM #12
DK, I'm going to have to disagree...the standard "brake fluid resistant" seal material is EPDM.
....which petroleum-based oil swells and rots...
....however a system purpose-built with other materials would be a perfect application for reasons listed.
Clark uses Bendix components...must be some sort of small auto application they adapted the parts from, but I see a "generic" master cylinder on ebay a lot that fits many many models, Clark, Hyster, etc.
07-11-2008, 09:10 PM #13
Pictures and everything! Thanks everyone!
07-16-2008, 05:26 AM #14
Matt you are not the only one who hates that inching feature, it only works on smooth flat floors, otherwise it is good way to roll into the side of a truck or drop a precarious load. Also if the brakes get out of adjustment the inching feature gets more and more out of sync.
As for using hydraulic oil (citreon spec LHM), been there as matt mentioned EPDM doesn't like it (swells)
I am encountering a variant of that problem currently after using toyota spec brake fluid in my forklift.
08-18-2010, 09:41 AM #15
new guy here i realize this is a older thread but could really use some help with the brake system on my yale 6k "YARDBIRD" lift vintage 1960/duell air tires. if you can help pm me thanks!